Though sometimes it's just something that reminds me. Once I had a notion for a story where the villain keeps reading Tarot cards, which accurately predict the future, if you read the cards right -- except he keeps mistaking who each figure is.
You may notice that it's an abstract idea, in that the only thing it tells is one habit of the villain's, and the sky is the limit for the events it could foretell.
Which means it really needs to be introduced to another idea (or several) to form a story. The problem being, it doesn't like any other ideas I've had at a time when I remember it.
Did manage to write one story about a plot bunny like this one about a decade -- maybe fifteen years -- after I first had it. The gap can be annoying.